Various techniques are known to provide a precision finish without introducing flaws to the finished surface. It is known to apply abrasive particles of diamond blended with other abrasive particles such as aluminum oxide or silicon carbide in a finishing or rubbing tape which has debris-collecting pockets (Japanese Laid Open application No. 130168/87, published Jun. 12, 1987). Furthermore, it is known to provide a surface finishing tape which has at least two abrasive layers each with different grinding properties (Japanese Laid Open Application No. 109084/89, published Apr. 26, 1989).
It is also known to make an abrasive sheet or polishing sheet containing an abrasive layer divided into discrete blocks by a network of grooves (U.S. Pat. No. 4,751,797).
The surface finishing tapes of the prior art generally utilized premium abrasive grains such as diamond or cubic boron nitride abrasive particles but such tapes are less effective because they contain the premium abrasive grains distributed throughout the thickness of the abrasive layer. Since it is only the surface abrasive grains that do the actual surface finishing, the premium abrasive grains contained within the abrasive layer were generally never afforded an opportunity to contact the work piece being finished.
Usually because of the high cost of the more premium abrasive material, it is desirable to optimize its utility in a surface finishing tape. While some of these references attempt to optimize the performance of the more premium abrasive material (diamond or cubic boron nitride), such attempts have had minimal effectiveness.
The layering of different abrasive grains on a surface finishing tape also has its drawbacks because such layering requires continued adhesion during use of a top layer onto a base layer which could separate in use to minimize the effect of the premium abrasive in the upper layer or introduce flaws as the top layer is delaminating.